Tip: You can also upload mp4 or webm videos (up to 1GB per file) directly to the editor and place them on the page.
For details, see Video box features and how to use them.
When doing so, please note the in-editor storage limits for each plan.
Issue
When embedding external videos such as YouTube or Vimeo, placing an Embed box as-is can leave empty space along the top and bottom or the left and right.
Solution
You can adjust the empty space around the video by setting the Embed box to a width of 200% and a height of 110vh.
Even with this setting, empty space may still appear on the sides or top and bottom when the screen width exceeds a certain size.
In that case, setting the height larger than 110vh can help reduce the empty space, but the video will be scaled up accordingly.
Keep in mind that background videos are also affected by the specifications of YouTube or Vimeo, so empty space may appear depending on the screen width.